Sync Tailscale hosts to route53

update_ts_dns.py

#!/usr/bin/env python
#
# Sync your tailscale hosts to a route53 hosted zone.
#
import json
import platform
import subprocess
import boto3
import click

ZONE_ID = ""
DOMAIN = ""


if platform.system() == "Darwin":
    TSCMD = "/Applications/Tailscale.app/Contents/MacOS/Tailscale"
else:
    TSCMD = "tailscale"


def get_ts_hosts():
    """Get hosts list from taillscale. Slight gotcha that this is
    divided into "Self" and "Peers", so we grab both."""

    tshosts = {}
    tsjson = json.loads(
        subprocess.run(
            ["{} status --json".format(TSCMD)], shell=True, capture_output=True
        ).stdout
    )
    for key, value in tsjson.items():
        if key == "Self":
            tshosts[value.get("HostName").lower()] = value.get("TailAddr")
        elif key == "Peer":
            for _, peerdict in value.items():
                tshosts[peerdict.get("HostName").lower()] = peerdict.get("TailAddr")
    return tshosts


def get_r53_hosts(zone_id):
    """ in which we get a list of A records in our zone """

    client = boto3.client("route53")
    rrsets = client.list_resource_record_sets(HostedZoneId=zone_id)
    r53_records = {}
    for rrset in rrsets["ResourceRecordSets"]:
        if rrset["Type"] == "A":
            r53_records[rrset["Name"]] = rrset["ResourceRecords"][0]["Value"]
    return r53_records


@click.command()
@click.option("--domain", type=str, default=DOMAIN)
@click.option("--zone-id", type=str, default=ZONE_ID)
def main(domain, zone_id):
    """ main logic """
    client = boto3.client("route53")
    changes = []
    tshosts = get_ts_hosts()
    r53_records = get_r53_hosts(zone_id)
    for host, ip in tshosts.items():
        hostname = "{}.{}.".format(host, domain)
        if hostname in r53_records:
            if not ip == r53_records[hostname]:
                print(
                    "{} exists, but ips don't match r53 {} vs ts {}".format(
                        hostname, r53_records[hostname], ip
                    )
                )
                changes.append(
                    {
                        "Action": "UPSERT",
                        "ResourceRecordSet": {
                            "Name": hostname,
                            "Type": "A",
                            "TTL": 300,
                            "ResourceRecords": [
                                {"Value": ip},
                            ],
                        },
                    }
                )

            else:
                print(hostname, "is correct")
        else:
            print("Need to add", hostname)
            changes.append(
                {
                    "Action": "CREATE",
                    "ResourceRecordSet": {
                        "Name": hostname,
                        "Type": "A",
                        "TTL": 300,
                        "ResourceRecords": [
                            {"Value": ip},
                        ],
                    },
                }
            )

    if changes:
        _ = client.change_resource_record_sets(
            HostedZoneId=zone_id, ChangeBatch={"Comment": "string", "Changes": changes}
        )


if __name__ == "__main__":
    main()